A4 Stainless Steel Aluminum Flat Sealing Washers are supplied to DIN 7603 Type A. The grade provides superior, including marine and chloride environments and is largely non-magnetic; the practical service range is approx. -200 °C to +400 °C, subject to the property class and the joint. Property data, grade comparison and the full size table follow.
Why Choose A4 Stainless Steel for Aluminum Flat Sealing Washers
Specified for marine, coastal and chemical applications. For aluminum flat sealing washers, this matters when superior, including marine and chloride environments is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80 |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
| Corrosion characteristic | Superior, including marine and chloride environments |
Corrosion Behavior in Service
A4 (316) adds 2–3% molybdenum to the A2 (304) composition, which dramatically improves resistance to chloride-pitting corrosion. For Aluminum Flat Sealing Washers in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Galvanic & Galling Considerations
For stainless aluminum flat sealing washers the compatibility question is galvanic rather than galling: joined to aluminum or galvanized steel in wet service, stainless drives corrosion of the less-noble metal. Isolate with a coating, sleeve or non-conductive washer where the joint sees moisture. Note also that stainless is softer than hardened carbon steel, so where the part carries a wear or shear duty, check the load against the grade before substituting.
Using Stainless Fasteners in Aluminum
Stainless steel is more noble than aluminum, so in the presence of an electrolyte — rain, condensation, salt spray — the aluminum becomes the anode and corrodes at the joint. The effect is driven by the area ratio: a small stainless fastener in a large aluminum section is normally acceptable, while a large stainless fastener in thin aluminum is not. Where the joint is wet, isolate the two metals with a coated or nylon washer and a sealant, or specify an aluminum or coated fastener instead.
Sizes of Aluminum Flat Sealing Washers Available in A4 Stainless Steel
| For bolt size | Pitch (mm) | Inside diameter (mm) | Outside diameter (mm) | Thickness options (mm) | Material | Reference standard |
|---|---|---|---|---|---|---|
| M8 | 1.0 | 8.2 | 11.4 | 1.0 / 1.5 / 2.0 | aluminum | DIN 7603 Type A |
| M10 | 1.0 | 10.2 | 13.4 | 1.0 / 1.5 / 2.0 | aluminum | DIN 7603 Type A |
| M12 | 1.5 | 12.2 | 15.9 | 1.0 / 1.5 / 2.0 | aluminum | DIN 7603 Type A |
| M14 | 1.5 | 14.2 | 17.9 | 1.0 / 1.5 / 2.0 | aluminum | DIN 7603 Type A |
| M16 | 1.5 | 16.2 | 19.9 | 1.0 / 1.5 / 2.0 | aluminum | DIN 7603 Type A |
| M20 | 1.5 | 20.2 | 23.9 | 1.0 / 1.5 / 2.0 | aluminum | DIN 7603 Type A |
| M30 | 1.5 | 30.3 | 35.9 | 1.0 / 1.5 / 2.0 | aluminum | DIN 7603 Type A |
| M48 | 2.0 | 48.3 | 54.9 | 1.0 / 1.5 / 2.0 | aluminum | DIN 7603 Type A |
